Osteosarcoma occurs in the region of the bone (the ends) where cells are actively replicating resulting in growth and lengthening of the bone. The presence of cancer necessitates the surgical removal of the cancerous bone, typically involving the joint, preventing further growth in this region. Limb salvage surgery is often performed in such cases and requires the use of an extension device which serves as a prosthetic replacement for the removed bone as well as allowing for extension, mimicking normal growth. It is also applied in, for example, patients with trauma wounds such as may be caused by gunshots, accidents and explosive devices.
There are very few devices that perform limb lengthening. These devices need minimal surgical procedures to lengthen. More recent devices obviate the need for surgery to lengthen. Only recently, motorised devices were introduced into the market, but these utilise permanent magnets internal to the device and cumbersome and heavy external induction coils to operate the motors. Also, microcontrollers are used to control operation of the motor to ensure precise incremental extension is achieved. These, however, limit the type of sterilisation that can be performed on the endoprosthesis and patient imaging or diagnostic methods that can be used to those which entail minimal or no radiation as radiation causes the contents of many memory types to be damaged. This includes the Flash and EEPROM used to store programs in the vast majority of microcontroller devices. Furthermore, these microcontrollers rely on measurements made by sensors placed on the devices to control the operation of the motor to achieve a desired extension.